The present invention relates to a dispensing member for dispensing a fluid, which dispensing member is designed to be mounted on the neck of a container. Conventionally, such a dispensing member comprises a body defining a chamber, an actuating rod provided with a pusher, a piston mounted on the actuating rod to slide in leaktight manner in the chamber, an inlet valve, and an outlet valve. By depressing the pusher, the piston is moved, thereby reducing the volume of the pump chamber, and thereby putting the fluid contained therein under pressure. The inlet valve closes and the outlet valve opens so as to deliver the fluid from the chamber to the outside.
In the prior art, numerous dispensing members already exist such as pumps, in which the outlet valve is situated inside the pump chamber and is mounted to slide on the actuating rod. In which case, the piston is formed by sleeving whose outside periphery defines a sealing lip serving to slide in leaktight manner against the inside wall of the body. In addition, the sleeving slides on the actuating rod so as to cover and uncover selectively one or more outlet orifices communicating with an internal duct formed inside the actuating rod. Naturally, in that type of dispensing member, the outlet orifice is situated on the pusher so that it moves therewith. That type of dispensing member is described, in particular, in Document WO 95/29016. The piston is urged by a spring that abuts at one end against the piston sleeving, and at the other end against an abutment collar formed by an actuating rod.
Unfortunately, that type of pump suffers from the disadvantage that the outlet valve member is coupled directly to the piston. It is therefore not possible to create or to take advantage of a ratio effect which would make it possible either to stiffen or to slacken operation of the pump, and in particular opening the pump outlet valve.
To make this possible, the present invention provides a fluid-dispensing member comprising:
a body defining a chamber;
an actuating rod provided with a pusher;
a piston mounted on the actuating rod to slide in leaktight manner in the chamber;
an inlet valve; and
an outlet valve;
the outlet valve comprising a differential piston that can be moved under the action of the pressure exerted on the fluid by the piston against the action of a spring which abuts at one end against the differential piston, and at its other end against the pusher. The piston and the differential piston are thus totally dissociated from each other, so that each of them moves separately. In other words, they may have strokes and diameters that are different. For example, the differential piston may have a diameter that is larger than the diameter of the piston that is mounted to slide in the chamber.
According to a characteristic of the invention, said differential piston is mounted to slide in the body. Advantageously, the body defines a cylindrical section in which the differential piston is slidably received, said cylindrical section being provided with a through hole that can be closed off selectively by said differential piston. In which case, the dispensing member has a stationary spray, i.e. it is provided with a dispensing orifice which does not move with the rod and with the pusher.
In a practical embodiment, a ferrule is engaged in the body to define the rest position of the piston, said differential piston being urged against said ferrule by the spring. Advantageously, the differential piston is mounted to slide in leaktight manner on cylindrical sleeving formed by the ferrule. The ferrule performs two functions, namely it acts as an abutment for the piston in the rest position, and as an abutment for the differential piston, also in the rest position. In addition, the cylindrical sleeving of the ferrule also serves as guide means for guiding the actuating rod in order to keep it in alignment.
In an embodiment, the differential piston is disposed between the pusher and the ferrule. In addition, the spring is situated outside the chamber. Furthermore, the differential piston is situated outside the chamber.